This invention relates to a fuel rail assembly that is used to deliver fuel to individual cylinders of an internal combustion engine.
In certain electromagnetic fuel injectors the fuel inlet is located such that fuel is introduced radially of the injector longitudinal axis. Such injectors are sometimes called "side-feed" or "bottom-feed" injectors, and one significant benefit of using these types of injectors is a reduction in the size of the packaging envelope in the engine compartment of an automobile.
For testing and installation purposes, automobile manufacturers desire electromagnetic fuel injectors to be part of a self-contained fuel rail assembly which can be mounted as a unit to an engine. A fuel rail assembly for side- or bottom-feed injectors does not readily lend itself to the metal fabrication techniques commonly used at present in fuel rail manufacture. Fabrication of a fuel rail for side- or bottom-feed injectors by using composite (plastic/glass/mineral) fabrication procedures is therefore desirable. It is toward such a composite fuel rail assembly for side- or bottom-feed electromagnetic fuel injectors that the present invention is directed.
One significant difference that typically exists between a "top-feed" injector and a side- or bottom-feed one is that the relative proportions are appreciably different. Overall, a side- or bottom-feed injector is generally shorter but not narrower than a top-feed injector. A necessary consequence of such a fact is that a fuel rail socket which receives a side- or bottom-feed injector must, at least in certain regions, be greater in diameter than a comparable socket for a top-feed injector. Since injectors for a given usage application are often exposed to comparable fuel pressures regardless of injector type, an injector-receiving socket of a fuel rail that is dimensioned for acceptance of a side- or bottom-feed type injector is apt to incur substantially higher maximum pressure-induced hoop forces than would be the case if it were dimensioned for acceptance of a top-feed type injector. In order to guard against unacceptably high magnitudes of maximum stress in the socket, the wall thickness of each region of the socket must be sufficiently large that the anticipated maximum stress that will occur therein is kept to a tolerable level. Since the typical socket also has multiple shoulders that create regions of different diameters in the socket, it becomes impossible to maintain a reasonably even stress field throughout the socket unless the socket wall thickness of each different diameter region is made unique to that particular region.
Yet, an important consideration which must be taken into account in the successful application of composite molding technology to the fabrication of a fuel rail assembly for an automotive internal combustion engine is the maintenance of generally uniform wall thickness throughout. In the absence of such maintenance, the resulting product may be prone to unacceptably high molded-in stresses and to unacceptably large deformation due to uneven shrinkage. Hence, although not all regions of a fuel rail socket may necessarily experience the same maximum hoop forces, successful molding considerations are likely to result in the requirement that thicknesses of certain regions which experience lower maximum forces than other regions be significantly greater than would be mandated by stress considerations if only the latter held sway. Therefore, for any given fuel rail configuration, the total amount of composite actually molded per rail is greater than that required on the basis of stress considerations alone. Accordingly, there exists a potential for a more efficient use of composite in a molded fuel rail, and it is that potential which is tapped by the present invention.
After an injector has been seated in its fuel rail socket, it is desirable that the injector be mechanically retained or captured in some manner. One aspect of the invention involves the use of such a mechanical retention for the additional purpose of strengthening the socket at a region of maximum hoop force in such a way that a molded composite fuel rail may make more efficient use of composite material. Favorable cost and weight implications accrue.
Another aspect of the invention involves a method for fabricating the mechanical injector-retention part and joining it to the injector-containing socket.
A further aspect of the invention relates to the construction of the joint which the injector-retention part provides between the injector-containing socket and an electrical connector plug that connects an electric control circuit to the electrical terminals of the injector when the fuel rail is functionally installed on an engine.
The foregoing, together with further details and advantages of the invention, will be seen in the ensuing description and drawings, which present a presently preferred embodiment according to the best mode contemplated at this time for the practice of the invention.